The invention concerns a method for the production of adsorption material from brown algae and its application to the adsorption of harmful substances such as heavy metals, hydrocarbons and the like substances from waste water.
According to this classification a similar method is already known from the Japanese patent abstract JP 1-15 133 A2, C-592, dated 2 May 1989, Vol. 13/No. 187. However in this patent precious metals such as gold, silver and platinum are collected with the aid of encapsulated but otherwise untreated algae. After this the metals are extracted with a special solvent (e.g. mercaptoethanol). For encapsulation of the algae polymer substances such as polyacrylamide and gelatine are used.
However, due to their poor binding ability precious metals possess adsorption properties which are completely different to the heavy metals or even hydrocarbons which are to be extracted by this invention.
In the Japanese patent there is no special information about the production of the algal material.
In addition to this, a publication in "Biotechnology and Bioengineering", Vol. 33, p. 823-831, 1989, by authors Kuyucak and Volesky should be mentioned. In this article the suggestion is made to make use of the adsorption ability of a brown alga, Ascophyllum nodosum, to adsorb the heavy metal cobalt. However, other heavy metals were not examined. In this publication special mention is made of the fact that when the alginate is extracted from the adsorption material the cobalt uptake by the biomass decreases by 91%. So this method should be avoided. Essentially, the method described by Kuyucak and Volesky corresponds to the normal alginate production in which at present considerable amounts of residual material are left.
It is also known to the experts working in this field that living microscopic and macroscopic algae can bind heavy metals to their surfaces and can also take them up to a certain extent after a longer period of reaction time. This adsorption of heavy metals can also be effected by dead (dried or extracted) biomass of the algae, as described above. The inventor of the method put forward here has established that in particular cultivated microscopic brown algae have good heavy metal adsorbing properties. However, a disadvantage of these microscopic algae which are cultivated in the laboratory is that they are very expensive to produce due to the complex technical cultivation apparatus (fermenters).
In the production of alginates, however, large quantities of macroscopic brown algae are left over and are a cheap waste product.
Thus the aim of the invention is to develop a method for preparing and cleansing macroscopic brown algae, and also to investigate any further technical application, in particular with regard to the residual biomass of brown algae after the commercial extraction of alginates.
By these means the high cost of production of biomasses can be saved if for example Laminaria-, Ascophyllum-, Fucus-, Macrocystis- and Nereocystis species are used. These algae are now being collected on the coasts of different countries in large quantities for the production of alginates, and are prepared and pressed out under alkaline conditions. The liquid extract thus obtained contains the alginates which for instance are used as swelling agents. Alginates are polysaccharides with an acid character.
As a result of extraction by pressing following rough crashing, large quantities of wet and compact residual biomass are left. These contain mostly cell wall material and also considerable amounts of intact, i.e. undamaged cells, but also other substances which are still soluble such as mineral salts, proteins, soluble polysaccharides, odour substances and many others. This biomass is at present partly used as fertilizer on fields. But this is not without problems, as this material develops unpleasant smells when it decomposes. This already sets in particularly during storage.
Inspite of the known adsorption properties this residual biomass cannot be employed as adsorption and filter material for purifying water to gain drinking water from used water as the soluble substances are washed out of the material. Moreover, this material can only be stored for a short time before it decomposes and starts to smell.